JPH0373335B2 - - Google Patents

Description

[Detailed Description of the Invention] Conventionally, as a method for adjusting the pore diameter of a molecular sieve carbon material, a molecular sieve carbon material having pores with a pore diameter of approximately 5 Å is treated with nitrogen gas containing benzene at a temperature of 800 to 900°C. A method of reducing the pore diameter by depositing carbon produced by the thermal decomposition of benzene on the pore walls (SVMoore, et al: Carbon, 15,
177 (1977)). Another method is to adsorb ethylbenzene, styrene, etc. at a low temperature onto a molecular sieve carbon material with pores of approximately 5 Å in diameter, and then heat treat the material at a temperature of 400°C to reduce the pore diameter (Chihara, et al. Carbon, 17, 339 (1979)) and the like are publicly known.

However, in the above method, in order to reduce the pore diameter without reducing the pore volume of the molecular sieve carbon as a raw material as much as possible, it is necessary to vapor deposit carbon at the entrance of the pores. Therefore, it is quite difficult to control the reaction temperature and the amount of vapor deposition.

Focusing on such drawbacks, the present invention uses carbonaceous adsorbent particles consisting of pores with a pore diameter of approximately 6 Å, and uses water as an impregnating agent to absorb an organic substance that is water-soluble at room temperature, such as sulfite pulp waste liquid, starch paste, etc. The pore size is approximately 3.3 by dipping it in a diluted solution for a predetermined time at room temperature, separating it, drying it, and heating it under predetermined conditions in an inert gas atmosphere using a heating furnace. We invented a method for preparing carbonaceous adsorbents with pores of ~4.3 Å.

The details of the invention will now be described.

A carbonaceous adsorbent with a particle diameter of 2 to 3 mmφ and a pore diameter of approximately 6 Å was used as an impregnating agent, such as sulfite pulp waste liquid,
An organic substance (specific gravity approximately 1.2 to 1.17) that is water-soluble at room temperature, such as starch paste, is diluted with water to 2 to 4 times its volume, and is immersed in the solution for 4 to 6 hours at room temperature, then separated and dried. Thereafter, this is heated in a heating furnace at a temperature of 200 to 500° C. for 1.5 to 4 hours under an inert gas atmosphere.

When diluting the stock solution of impregnating agent with water, if the volume is less than twice the volume, the liquid concentration will be high and sticky. It is difficult to form clusters by adhesion. Moreover, if the volume is 4 times or more, the liquid concentration is too low and the impregnating effect is poor. Regarding impregnation time,
If the time is less than 4 hours, the amount of impregnation will be insufficient, and if the time is more than 6 hours, no significant improvement in the impregnating effect will be observed. Regarding the heat treatment temperature, when the heat treatment temperature is 200°C or lower, both the thermal curing and thermal decomposition effects of the dried impregnated adsorbent particles are extremely small, so the pore volume of the obtained adsorbent is extremely small. If the temperature is 500°C or higher, thermal decomposition will proceed excessively and the pore size will increase. Regarding the heating time, if the heating time is 1.5 hours or less, both the thermal curing and thermal decomposition of the dried impregnated adsorbent particles are insufficient, and if the heating time is 4 hours or more, no significant effect is observed. Note that within the limits of the present invention, the heating time can be shortened as the heating temperature increases. In this way, the pore diameter is adjusted to 3.3-4.3 Å. Next, details of the present invention will be described below.

The carbonaceous adsorbent particles used in the present invention have a particle size of 2 to 3
mmφ 760mm at 25℃ using carbon dioxide (minimum molecular diameter 3.3Å), ethane (minimum molecular diameter 4.0Å), n-butane (4.3Å), isobutane (minimum molecular diameter 5.0Å)
When conducting an adsorption test with Hg adsorption pressure, the adsorption amounts were 80.0 mmg/g, 37.5 mmg/g, and 15.0 mmg/g, respectively.
g, 5.4 mmg/g. Since a small amount of isobutane is adsorbed, the pore diameter is somewhat larger than 5.0 Å, and the pore diameter is estimated to be approximately 6 Å.
In the examples of the present invention, the above carbonaceous adsorbent particles are simply abbreviated as adsorbent particles.

Example 1 Adsorbed granules were impregnated by immersing them in a solution prepared by diluting starch paste as an impregnating agent to 4 times the volume with water at room temperature for 6 hours.
It was separated and dried at 110° C. for 2 hours, and then heated in a heating furnace at 200° C. for 4 hours in a nitrogen gas atmosphere. Product yield is based on dry impregnated sorbent granules.
It was 98.6% (weight).

In order to examine the pore size of this product, adsorption tests were conducted at 25°C and an adsorption pressure of 760mmHg using different gases such as carbon dioxide, ethane, normal butane, and isobutane. As a result, carbon dioxide,
The adsorption amounts of ethane, n-butane, and isobutane are 50.0 mmg/g, 5.7 mmg/g, and 1.0 mmg/g, respectively.
g, 0.5 mmg/g. Adsorption of normal butane (minimum molecular diameter 4.3 Å) and isobutane (minimum molecular diameter) is extremely small. From this, it is estimated that there are almost no pores larger than approximately 4.0 Å in pore diameter in this product.

Example 2 Adsorbent granules were impregnated by immersing them in a solution of starch paste as an impregnating agent diluted to 4 times the volume with water at room temperature for 6 hours, and then separated and dried at a temperature of 110°C for 2 hours.
It was heated at a temperature of 400° C. for 2 hours in a nitrogen gas atmosphere using a heating furnace. The product yield was 97.6% (by weight) based on the dry impregnated adsorbent granules.

In order to examine the pore size of this product, an adsorption test similar to that in Example 1 was conducted. As a result, the adsorption amounts of carbon dioxide, ethane, n-butane, and isobutane were 60.0 mmg/g, 10.0 mmg/g, and 1.8 mmg/g, respectively.
It was 0.6 mmg/g.

The adsorption amount of normal butane and isobutane is extremely small. Therefore, the pore diameter of this product is approximately
It is estimated that there are almost no pores larger than 4.0 Å.

Example 3 Adsorbent granules were impregnated by immersing them in a solution of sulfite pulp waste as an impregnating agent made up to twice the volume with water at room temperature for 5 hours, separated and dried at a temperature of 120°C for 2 hours. was heated at a temperature of 300° C. for 3 hours in a nitrogen gas atmosphere using a heating furnace. The product yield was 92.5% (by weight) based on the dry impregnated adsorbent granules.

In order to examine the pore size of this product, an adsorption test similar to that in Example 1 was conducted. As a result, the adsorption amounts of carbon dioxide, ethane, n-butane, and isobutane were 77.0 mmg/g, 2.07 mmg/g, and 0.6 mmg/g, respectively.
g, 0.5 mmg/g.

Ethane (minimum molecular diameter 4.0Å), normal butane,
The amount of isobutane adsorbed is small. Based on this, it is estimated that there are almost no pores larger than approximately 3.3 Å in pore size in this product.

Example 4 Adsorbent granules were impregnated by immersing them in a solution of sulfite pulp waste diluted to twice the volume with water as an impregnating agent for 4 hours at room temperature, separated and dried at a temperature of 120°C for 2 hours. This was heated at a temperature of 500° C. for 1.5 hours in a nitrogen gas atmosphere using a heating furnace. The product yield was 94.0% (by weight) based on the dry impregnated adsorbent granules.

In order to examine the pore size of this product, an adsorption test similar to that in Example 1 was conducted. As a result, the adsorption amounts of carbon dioxide, ethane, n-butane, and isobutane were 80.0 mmg/g, 17.4 mmg/g, and 2.1 mmg/g, respectively.
It was 1.0 mmg/g.

The adsorption amount of normal butane and isobutane is small. From this, it is estimated that there are almost no pores larger than approximately 4.3 Å in pore diameter in this product. Next, as a reference, Example 5 shows a case where processing was performed under conditions other than those specified in the present invention.

Example 5 Dry impregnated adsorbent particles obtained under exactly the same conditions as Example 4 were heated in a nitrogen gas atmosphere using a heating furnace.
Heated at a temperature of 600°C for 1.5 hours. As a result, the product yield was 89.8% (weight) based on the dry impregnated and adsorbed particles.

In order to examine the pore size of this product, an adsorption test similar to that in Example 1 was conducted. As a result, the adsorption amounts of carbon dioxide, ethane, n-butane, and isobutane were 80.0 mmg/g, 32.0 mmg/g, and 17.0 mmg/g, respectively.
It was 5.0 mmg/g.

The adsorption amount of normal butane is rather large, but the adsorption amount of isobutane is considerably smaller, less than one-third of that. As a result, the pore size of this product is 5.0.
It is estimated that there are almost no pores that are slightly larger than about 6 Å. What is noteworthy is that it has almost the same adsorption characteristics as the carbonaceous adsorbent particles used as the raw material in the present invention.

As described above, according to the present invention, the pore size of a carbonaceous adsorbent having pores with a pore size of about 6 Å can be easily and easily adjusted.
A carbonaceous adsorbent with pores of 3.3 to 4.3 Å can be prepared.

Claims (1)

[Claims] 1. Carbonaceous adsorbent particles consisting of pores with a pore diameter of approximately 6 Å are impregnated with an organic substance that is water-soluble at room temperature, such as sulfite pulp waste liquid, starch paste, etc., diluted with water to 2 to 4 times the volume. A fine carbonaceous adsorbent characterized in that it is impregnated by soaking in water for 4 to 6 hours at room temperature, separated and dried, and then heated in a heating furnace at a temperature of 200 to 500°C under an inert gas atmosphere. How to adjust pore size.